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    Edge functionalisation of graphene nanoribbons with a boron dipyrrin complex : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nanoscience at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Way, Ashley Jacqulyne
    Chemical modification can be used to tune the properties of graphene and graphene nanoribbons, making them promising candidates for carbon-based electronics. The control of edge chemistry provides a route to controlling the properties of graphene nanoribbons, and their self-assembly into larger structures. Mechanically fractured graphene nanoribbons are assumed to contain oxygen functionalities, which enable chemical modification at the nanoribbon edge. The development of graphene nanoribbon edge chemistry is difficult using traditional techniques due to limitations on the characterisation of graphene materials. Through the use of a chromophore with well-defined chemistry, the reactivity of the edges has been investigated. Small aromatic systems were used to understand the reactivity of the boron dipyrrin Cl-BODIPY, and with the aid of spectroscopic and computational methods, the substitution mechanism and properties of the compounds have been investigated. The synthetic procedure was then applied to graphene nanoribbons. Results from infrared and Raman spectroscopy studies show that edge-functionalisation of graphene nanoribbons with BODIPY was successful, and no modifications to the basal plane have been observed.
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    At the cutting edge : structural analysis and chemical modification of the edges of mechanically cleaved graphene nanoribbons : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nanoscience at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Dykstra, Haidee Michaela
    The first decade of the new carbon nanomaterial graphene has been a time of great discovery and excitement as the exceptional properties of this material were uncovered and its promise for numerous applications realised. The unique properties of graphene, including its exceptional electronic structure, are now well-established, and investigations into how these properties can be manipulated and exploited are rapidly taking off. This research contributes to the emerging field by exploring the structure and chemistry of the edges of mechanically cleaved graphene nanoribbons; groundwork for the future development of edge-modified nanoribbons that could be used to form selfassembled graphene nanoribbon composite structures with potential for devices in solar energy conversion. For this purpose, a Raman microscope was built that enabled for various aspects of the structure of graphene nanoribbons to be probed, in particular the geometry and smoothness of the edges, which have important implications for the specific reactivity of the edge carbon atoms. Chemical approaches for the specific functionalisation of the edges of the nanoribbons were developed, involving reactions tailored to the reactive groups present at the edges, and these were found to be highly successful and selective.
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    SEIRAS of functionalised graphene nanomaterials : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nanoscience at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Fisher, Ewan
    Graphene exhibits many excellent properties, but many next-generation devices require post chemical treatment to introduce structural confirmations, defects or a particular impurity to obtain functionality. The understanding of these defects and the manifestation of desirable properties using chemical modification is a fundamental problem with low defect graphene as the small number of functional groups provides insufficient signal intensity for many characterisation techniques. Metallic nanoparticles are at the centre of plasmonics for enhancing optical signals. This work is a unique undertaking for the examination of novel Steglich esterification chemistry that is performable on graphene as well as providing insight into the native edge structure of as-produced graphene flakes using surface enhanced infrared reflection absorption spectroscopy (SEIRAS) to characterise covalently functionalised graphene materials. Two methods of producing graphene flakes that are relatively low or high in defects have been developed to contrast the effect that inherent defects have on the macroscopic physical and spectroscopic properties. Ultraviolet-visible spectroscopy in conjunction with Raman, electron and atomic force microscopy was used to elucidate the origins and density of defects to draw conclusions on how graphene’s macroscopic properties manifest from atomic level defects. Discussions of infrared vibrational spectroscopy are carried out before an extension to SEIRAS where the use of near-field plasmon and phonon modes are attributed to observed optical enhancements. The experimental preparation is focused towards understanding the role nanoparticles play in SEIRAS of graphene and is discussed such that other graphene researchers can recreate SEIRAS for their graphene research. TEM is used to characterise the variety of nanoparticle shapes and geometries as well as provide topological insights on nanoparticles adsorbed to flakes of graphene. SEIRAS probes the defects native to graphene which confirms the presence of oxygen functionality. Steglich esterification reactions were utilised to successfully prepare a range of graphene materials with novel covalently bound functional groups as confirmed by SEIRAS. Covalent chemistry was extended to introduce a redox-active ferrocene derivative where SEIRAS was used to observe in real-time, the effect of interconversion of ferrocene to the ferrocenium cation. The foundations for the development of graphene-based solid state solar cells was the final focus of this work. Development and production of a potential photo-active layer was explored with Cl-BODIPY as the basis chromophore. Production of a flexible, electrically conductive substrate from graphene flakes was carried out, and tunnelling electron microscopy (TEM) was used to characterise topological and morphological surface features. The focus here was on covalent and physical absorption to graphene flakes. SEIRAS was used to confirm nucleophilic substitution (covalent) modification while STEM was used to confirm the uniformity of BODIPY on the substrate and chlorine atomic mapping to confirm physisorption.
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    Characterisation and functionalisation of mechanically fractured graphene nanoribbons : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nanoscience at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Brooke, Samuel James
    Graphene has been heralded as the supermaterial of the future, boasting incredibly high electron mobility, thermal conductivity, and physical strength – all contained within the world’s first true 2D material, only a single atom thick. Graphene nanoribbons (GNRs) broaden this potential further by demonstrating width-dependent band gaps due to confinement effects. In addition, the ability to define the edge geometry and dimensions of GNRs allows control over self-assembly of these novel carbon nanostructures. GNR synthesis has been broadly explored in literature, demonstrating both relatively high yields and atomic-scale precision. Rarely, however, are these two criteria achieved in the same technique. Longitudinal unzipping of carbon nanotubes (CNTs) generates large quantities of nanoribbon material at the expense of quality, while techniques such as chemical vapor deposition (CVD) and bottom up synthesis achieve truly astounding quality, but lack scalability. Recently, the synthesis of highly ordered GNRs with tunable dimensions and unique geometries has been demonstrated using mechanical fracturing of a block of graphite via simple microtomy techniques. This method offers a top-down approach to GNR synthesis providing highly ordered structure on a much larger scale than efforts to date. In this work, this technique has been altered to use a dry-cut method, and the structural and chemical properties of the material obtained therein have been extensively characterised, demonstrating increased quality, structural order, and quantities obtainable. Further, this work has demonstrated the functionalisation of these dry-cut materials both chemically via simple organic chemistries, and non-covalently utilising filamentous bacteriophage as a route towards biofunctionalisation.